1 - Define oriented grid then use the oriented grid
2 - Orient the design environment and use the orthogonal grid
The orange, persistent guidelines can even be round!
And of course in any angle you desire.
Do the following steps:
Drag the guideline onto the element, e.g. a wall. The guide will then snap into the correct angle. Then hover over the guideline and an orange orb will appear. This is its handle and you can then drag the guidline away from the element to the desired location.
Yikes. My bad. Somehow misread that.
Thats harder than I thought since the relative construction methods are somehow not available when making guidelines.
Anyway, a workaround would be to just use normal lines at first (since you can use the relative methods on them), and then use the orange guidelines, if you want them to persist.
If you just need them temporarily I'd go with the blue snap guides instead.
As usual there are different ways to handle your workflow. The guidelines do work, in parallel and perpendicular, but they take a short time before they appear. I use a one key shortcut for some constraints, mainly the parallel and the perpendicular one. This way I don't have to hover over an element and wait for the guideline to appear before I start drawing. Search for "constraint" in the keyboard shortcuts menu and set up the shortcuts you need. You'll probably have to override some default settings so be careful and choose some shortcuts you won't need or don't use. It does save some time.
Archicad 4.55 - 24 | HP Z800 | Dual Xeon X5667 | 48 GB RAM | Nvidia Quadro P1000 @ Windows 10 Pro x64